1. Field of the Invention
The present invention relates to a telephone communication method for a communication system allowing a plurality of telephone terminals to communicate via Internet or Intranet (Private IP (Internet Protocol) Network).
2. Description of the Background Art
Speech communication systems implemented by Internet include an IRC (Internet Relay Chat) server system referred to as Internetphone. A conventional telephone communication system using the IRC server system accommodates a number of gateways capable of accessing Internet. Telephone terminals are connected t o each of the gateways via respective subscriber lines so as to allow conversation to be held therebetween. A number server is connected to Internet and assigns a particular IP (Internet Protocol) address to the telephone number of each telephone terminal for a control purpose.
Before a telephone connection, a gateway requests entry registration for a telephone service of the number server. In response to the request, the number server assigns a particular IP address to each telephone accommodated in the gateway, Assume that after the assignment of the IP addresses one of the telephone terminals accommodated in the gateway sends a call request meant for another telephone terminal to the gateway. Then, the gateway inquires of the number server an IP address assigned to the telephone to be called. In response, the number server searches for the above IP address and sends it to the gateway. The gateway having received the IP address sends a call connection request to a gateway accommodating the telephone terminal designated by the IP address. As a result, the call is terminated at the telephone terminal to be called. The called telephone terminal sends an answer representative of the call connection to the gateway accommodating the calling telephone terminal via the gateway accommodating the called telephone terminal. Consequently, the calling terminal and called terminal are connected together and allowed to communicate with each other.
The conventional telephone communication procedure described above has the following problems left unsolved. First, while a particular IP address must be assigned to each telephone terminal, communication will become difficult in the future because the number of IP addresses is limited and short throughout the world. Second, the communication system inhibits communication from being held on telephone terminals other than those registered at the number server, so that it is not available for emergency calls.
It is therefore an object of the present invention to provide a telephone communication method allowing a plurality of telephone terminals to share a single IP address and thereby promoting the efficient use of the limited number of IP addresses.
It is another object of the present invention to provide de a telephone communication method implementing a telephone communication system available even for emergency calls.
A telephone communication method of the present invention is applicable to a network system including a plurality of gateways given respective IP addresses corresponding to the addresses of Internet, which includes a control line having a first and a second channel and a speech line having a first and a second channel, for holding communication with each other via Internet on the basis of the IP addresses, and a plurality of telephone terminals given respective telephone numbers for holding communication with each other via the gateways on the basis of the telephone numbers. The method begins with the step of preparing a name server connectable to the gateways via Internet for managing the names of the gateways, IP addresses respectively corresponding to the names, and office numbers respectively assigned to the gateways.
When a first telephone terminal outputs a connection request meant for a second telephone terminal, a first gateway accommodating the first telephone terminal is caused to access the name server via the first channel of the control line in response to a call originated on the first telephone terminal, and inquire the name server of the IP address of the second gateway by using the name corresponding to the office number assigned to the second gateway. The name server sends the IP address of the second gateway to the first gateway on the first channel of the control line. The first gateway selects the IP address of the speech line connected thereto and sends a call connection request to the second gateway on the second channel of the control line. The second gateway determines whether or not the second telephone terminal is busy, selects, if the second telephone terminal is idle, the IP address of the speech line, and returns the IP address selected to the first gateway, thereby setting up a connection between the first telephone terminal and the second telephone terminal. The first gateway transfers a speech signal received from the first telephone terminal to the second gateway on the speech line, and causes the second gateway to send the speech signal to the second telephone terminal.
Also, a telephone communication method of the present invention is applicable to a network system including a plurality of gateways given respective IP addresses corresponding to the addresses of Internet, which includes a control line having a first and a second channel and a speech line having a first and a second channel, for holding communication with each other via internet on the basis of the IP addresses, a plurality of switching systems given respective office numbers for holding communication with each other via the gateways on the basis of the office numbers, and a plurality of telephone terminals given respective telephone numbers for holding communication with each other via the gateways and switching systems on the basis of the telephone numbers. The method begins with the step of preparing a name server connected to the gateways via Internet for managing office numbers and names respectively given to the switching systems and IP addresses assigned to the gateways to which the switching systems are respectively connected. Subscriber data tables each is stored in a respective one of the gateways and has a division field storing division data showing whether an apparatus accommodated in the respective gateway is the telephone terminal or the switching system, and an office number field storing an office number assigned to the gateway and an office number assigned to the switching system accommodated in the gateway.
When a first telephone terminal outputs a connection request meant for a second telephone terminal, a first gateway accommodating the first telephone terminal accesses the name server via the first channel of the control line in response to a call originated on the first telephone terminal and a call originated on a first switching system accommodating the first telephone terminal, and inquire the name server of the IP address of a second gateway accommodating a second switching system accommodating the second telephone terminal by using the name corresponding to the office number assigned to the second switching system. The name server sends the IP address of the second gateway to the first gateway on the first channel of the control line. The first gateway selects the IP address of the speech line connected thereto and sends a connection request to the second gateway on the second channel of the control line. The second gateway searches division data of the subscriber data and searches for, if the division data is representative of a switching system, the line of a switching system at which the office number of the second switching system and the office number included in the subscriber data coincide. The second gateway having detected the line of the switching system determines whether or not the line of the switching system is busy, selects, if the line is idle, the IP address of the speech line, and return the IP address selected to the first gateway, thereby setting up a connection between the first switching system and the second switching system and therefore between the first telephone terminal and the second telephone terminal. The first gateway transfers a speech signal received from the first telephone terminal via the first switching system to the second gateway via the speech line, and then the second gateway sends the speech signal to the second telephone terminal via the second switching system.